If by voices you mean oscillator/trigger combinations, three - 2x Plaits and BIA. Otherwise, seven (Mangrove, STO, Dixie, Loquelic Iteritas). However, with Ears bringing other things into the system, I guess I could say eight.

If by voices you mean oscillator/trigger combinations, three - 2x Plaits and BIA. Otherwise, seven (Mangrove, STO, Dixie, Loquelic Iteritas). However, with Ears bringing other things into the system, I guess I could say eight.

Dozens—too many to calculate. My limitation would be summing: I’d run out of summing opportunities before I ran out of sound sources. The beauty of modular is that you can turn any suitable voltage fluctuation into a voice. Even a simple trigger signal is a voice, depending on what you do with it (e.g., run it into a reverb). Filters can be pinged or self-oscillate. Various switches and devices can be run at audio rates...

Errr.. some. Depends if I include drum voices, filters that can self-oscillate nicely, things like Disting MK.4 that has a bunch of oscillator and sample player modes etc.., as well as what's actually in the rack this week. Also, when you have things which can be used to cobble together envelopes, VCA behaviour, it's all a bit of a movable feast.

Moreover, two voices patched one way can easily collapse down to one with a couple of oscillators feeding it etc..

Good question, I hadn't realised how weird the answer is until I tried to formulate one. I could probably would out an answer, but I guarantee that after a couple of weeks of tinkering, I'd have a higher number once I'd worked out some cheats.

You mean like the theoretical maximum simultaneous number of sounds I could generate in my system by any means, including audio-rate triggering of sequencers, feedback loops around high-gain VCAS and other such modular voodoo?

If I *insist* that every voice have at least one envelope, a VCA, and a sequencing source, and all voices have a filter of some kind, no West-ish complex osc no-filter voices, then...15. I would need to take over every input on the patch bay to sum all those voices to the main studio mixer, but it's possible.

Meaning, if pressed, how many distinct, identifiable sounds could you generate at once in your rack?

There are so many ways to bend this, so many different permutations that I'm not going to try to figure it out.

Just looking at the Hertz Donut mk2, the obvious answer is one or two. But there are five outputs, and with clever sequencing and enough VCAs/LPGs, one could get five perceptually separate "voices" out of it. Or even mult the outputs through other processors to create even more voices...

So maybe VCAs are the limiting factor? Well, I only have one dual VCA and one dual LPG in my whole 12Ux114HP rack. But I've got modules with internal VCAs, I've got filters, I've got Maths... and I've got Bitwig Studio, which honestly acts as my "VCAs" quite often since I tend to play drone-ish voices with manual level control via my 16n Faderbank.

On a more practical level, I tend to run with 1-5 voices per recording, counting the modular, Lyra-8, Reface CS and rarer software voices. A "voice" is a bit arbitrarily defined even there.

I mean, I can patch quite a few different sounds up simultaneously, but now that I've downsized to a 7U case from my 14U, I feel like I come up to the limits of the system pretty often. I typically have about 4-6 different types of sounds going on, and I can surely do a bit more, but I have a very very limited system right now:

Let's see, the BIA is an all-in-one voice. And I also have Fracture, which is all-in-one. So there's 2 easy ones.
Then I have a Sinc Iter, and Lifeforms Primary oscillator. Those can be another 2-4 voices depending on if I want to take multiple outs from the lifeforms.
The Filter8 can be a voice in self-oscillation.
Then I have some noise sources and some LFO's that can be pushed to the audio range.. That could be another 3-4 voices.
Just Friends could be another 6 voices.. Batumi can technically be a voice..
Even on my 'limited' system, I can actually patch quite a few things. I have a WMD-PM mixer that has 8 inputs, and it's not hard to use them all if I want.

I guess in practice the main limitation for using it all simultaneously is the number of envelopes and VCAs I have: which is 2-channels of Maths, 1 channel from Contour1, and 2 from my Doepfer A142-2 dual env-controlled VCAs. (so 5 envelopes).
For VCAs I have a ModDemix (2 channels), XAOC Talllin (2 channels), The Doepfer A142-2 (2 Channels), and the WMD-PM (8 channels).
I guess I have more VCAs than envelopes, so envelopes is the practical limit today.

This was fun! I guess that anyone with a significant-sized system could do a LOT more. ha ha.

Dozens—too many to calculate. My limitation would be summing: I’d run out of summing opportunities before I ran out of sound sources. The beauty of modular is that you can turn any suitable voltage fluctuation into a voice. Even a simple trigger signal is a voice, depending on what you do with it (e.g., run it into a reverb). Filters can be pinged or self-oscillate. Various switches and devices can be run at audio rates...

This is the real answer. I looked at my modular grid to try and count but my head exploded first.

It's really about limiting factors. I wound up spending a fair amount of time analyzing my setup in terms of voices and realized I needed a better definition, so I've come up with three types of voice: sustaining, pitched percussion, and drums. One obvious limit is set by the signal sources available. Disregarding tricks like driving filters into resonance:
I have 10 VCOs capable of sustained tones, plus enough VCAs, LPGs and function generators to complete 10 sustaining voices and enough mixer inputs for 17.
I have 2 modules that are best at pitched percussion.
I have 4 simple drum modules.

So, 16?

Looking at it another way, I counted the voices by my ability to control them. I have 20 CV channels from my laptop-- sustained and pitched percussion require two (one as trigger), drums get by on one each, so the laptop controls 12 parts. I have a QuNexus and WX5 to control sustained voices and two sample and holds with clocks to bring that total up to 16 also.
Definitely 16.

Weird question indeed. I mean, I could probably squeeze 20 and a few voices out of my modular, but then, most of these wouldn't be interesting at all. Of course, for a melodic base structure, some of these "simple" voices really are used.
But the modular realm gets interesting when we stray off that path and create voices that we can't get out of the countless pre-built synth engines. Like when I made a monster bass voice that used I think eight modules, not counting the sequencer. That shook the dust out of my cans, but it ended up so "phat" there was no way to use it sensibly in any melody arrangement that I could have thought of. It was still cool.